Resin member and method for producing resin member

ABSTRACT

A resin member is formed from a resin material containing filler and an insulating base polymer as a main component. The resin member includes an alignment layer close to a surface of the resin member. The alignment layer includes the filler aligned in the surface direction and the base polymer filling the space between pieces of the filler. The alignment layer includes a carbonized portion that is carbonized matter of the base polymer, contains graphite, and provides electrical conductivity and thermal conductivity.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation application of InternationalApplication No. PCT/JP2019/028191 filed on Jul. 18, 2019, which is basedon and claims the benefit of priority from Japanese Patent ApplicationNo. 2018-136647 filed on Jul. 20, 2018 and Japanese Patent ApplicationNo. 2019-128420 filed on Jul. 10, 2019. The contents of theseapplications are incorporated herein by reference in their entirety.

BACKGROUND

The present disclosure relates to a resin member and a method forproducing the resin member.

Techniques for graphitizing the surface layer of a resin member to formcarbonized matter are conventionally known.

SUMMARY

A resin member according to the first aspect of the present disclosureis formed from a resin material containing filler and an insulating basepolymer as a main component. The resin member includes an alignmentlayer close to the surface of the resin member, and the alignment layerincludes filler aligned in the surface direction. The alignment layerincludes a carbonized portion that contains graphite.

A method for producing a resin member according to a first aspect of thepresent disclosure includes a molding step and a carbonization step. Inthe molding step, the resin material is molten, and molten resincorresponding to an area close to the surface of the resin member issubjected to shear stress and then solidified to form, close to thesurface, the alignment layer including the pieces of filler aligned inthe surface direction. In the carbonization step, the alignment layer isheat-treated, generating the carbonized portion including graphite.

A resin member according to the second aspect of the present disclosureincludes a resin material and has a base portion and a carbonizedportion. The base portion includes an insulating base polymer formedfrom a resin material and a filler stronger than the base polymer. Thecarbonized portion is provided in the outer surface of the base portion.The filler prevents the carbonized portion from being detached from thebase portion.

A method for producing a resin member according to the second aspect ofthe present disclosure is a method for producing a resin member, andincludes a preparation step and a carbonization step. The preparationstep includes preparing a base portion including an insulating basepolymer and filler stronger than the base polymer. The carbonizationstep includes heating the base portion to provide the outer surface ofthe base portion with a carbonized portion.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, and advantages of the presentdisclosure will be clearly apparent from the detailed descriptionprovided below with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a resin member according to a firstembodiment;

FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1;

FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2;

FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2;

FIG. 5 is a process diagram of a production method according to thefirst embodiment;

FIG. 6 is a cross-sectional view of a mold into which molten resin isbeing injected in a molding step of the production method according tothe first embodiment, illustrating the alignment state of filler nearthe interface between the mold and the molten resin;

FIG. 7 is a cross-sectional view of the mold in FIG. 6, illustrating thealignment state of molecular chains near the interface between the moldand the molten resin;

FIG. 8 is a diagram illustrating the a-b plane of graphite forming acarbonized portion in FIG. 4;

FIG. 9 is a cross-sectional view of a molded article with its alignmentlayer being irradiated with a laser beam in a carbonization step of theproduction method according to the first embodiment;

FIG. 10 is a perspective view of a resin member according to a secondembodiment;

FIG. 11 is an enlarged perspective view of a part of a carbonizedportion in FIG. 10;

FIG. 12 is a cross-sectional view taken along line XII-XII in FIG. 10;

FIG. 13 is a cross-sectional view of a molded article with its alignmentlayer being irradiated with a laser beam in a carbonization step of aproduction method according to the second embodiment;

FIG. 14 is a cross-sectional view of a molded article according to athird embodiment, illustrating recesses therein;

FIG. 15 is a cross-sectional view of a molded article according to afourth embodiment, illustrating recesses therein;

FIG. 16 is a cross-sectional view of a recess in a molded articleaccording to a comparative embodiment;

FIG. 17 is a cross-sectional view of a molded article according to afifth embodiment, illustrating recesses therein;

FIG. 18 is a cross-sectional view of a molded article according to asixth embodiment, illustrating recesses therein;

FIG. 19 is a perspective view of a resin member according to a seventhembodiment;

FIG. 20 is a cross-sectional view taken along line XX-XX in FIG. 19;

FIG. 21 is a photograph showing the cross section of FIG. 20;

FIG. 22 is a cross-sectional view corresponding to FIG. 20,schematically illustrating pieces of filler caught in carbonized matter;

FIG. 23 is a process diagram of a method for producing the resin memberaccording to the seventh embodiment;

FIG. 24 is a perspective view of a base portion prepared in apreparation step in FIG. 23;

FIG. 25 is a cross-sectional view taken along line XXV-XXV in FIG. 24;

FIG. 26 is a perspective view of the base portion being irradiated witha laser beam in a carbonization step in FIG. 23;

FIG. 27 is a cross-sectional view taken along line XXVII-XXVII in FIG.26;

FIG. 28 is a perspective view of a resin member according to an eighthembodiment;

FIG. 29 is a cross-sectional view taken along line XXIX-XXIX in FIG. 28;

FIG. 30 is a photograph showing the cross section of FIG. 29;

FIG. 31 is a perspective view of a base portion being irradiated with alaser beam in a carbonization step according to the eighth embodiment;

FIG. 32 is a cross-sectional view taken along line XXXII-XXXII in FIG.31;

FIG. 33 is a perspective view of a resin member according to a ninthembodiment;

FIG. 34 is a process diagram of a method for producing the resin memberaccording to the ninth embodiment;

FIG. 35 is a perspective view of a base portion prepared in apreparation step in FIG. 34;

FIG. 36 is a perspective view of the base portion after being rounded ina rounding step in FIG. 34;

FIG. 37 is a perspective view of the base portion being irradiated witha laser beam in a carbonization step in FIG. 34;

FIG. 38 is an enlarged photograph of the front of a resin memberaccording to a tenth embodiment;

FIG. 39 is a cross-sectional view taken along line XXXIX-XXXIX in FIG.38;

FIG. 40 is a process diagram of a method for producing the resin memberaccording to the tenth embodiment;

FIG. 41 is a perspective view of a molded article with its alignmentlayer being irradiated with a laser beam at the initial stage of acarbonization step in Example 1;

FIG. 42 is a perspective view of the molded article with its alignmentlayer being irradiated with a laser beam at the final stage of thecarbonization step in Example 1;

FIG. 43 is a photograph showing the edge of a carbonized portion formedin the alignment layer in the carbonization step in Example 1;

FIG. 44 is a photograph showing a carbonized layer, as viewed from anangle of 45 degrees, in a third area of the carbonized portion formed inthe alignment layer in the carbonization step in Example 1;

FIG. 45 is a photograph showing the cross section of the third-areacarbonized matter cut along the laser beam direction with the entireresin member, after the carbonization step, fixed with a casting madefrom epoxy resin in Example 1;

FIG. 46 is a photograph showing the edge of a carbonized portion formedin an alignment layer in a carbonization step in Example 4;

FIG. 47 is a diagram illustrating carbonized portions formed in analignment layer in a carbonization step in Example 5;

FIG. 48 is a cross-sectional view of the alignment layer of a moldedarticle and a metallic member with their contact interface beingirradiated with a laser beam in a carbonization step of a productionmethod in Example 13;

FIG. 49 is a cross-sectional view of the alignment layer and themetallic member with their contact interface carbonized in Example 13;

FIG. 50 is a cross-sectional view of the alignment layer of a moldedarticle and a metallic member with their contact interface beingirradiated with a laser beam in a carbonization step of a productionmethod in Example 14;

FIG. 51 is a cross-sectional view of the alignment layer and themetallic member with their contact interface carbonized in Example 14;

FIG. 52 is a perspective view of a molded article formed in anotherembodiment;

FIG. 53 is a perspective view of the molded article with a carbonizedportion formed in the other embodiment;

FIG. 54 is a perspective view of a plurality of resin members beingcombined with each other in the other embodiment;

FIG. 55 is a perspective view of the plurality of resin members with acovering formed in the other embodiment; and

FIG. 56 is a perspective view of a molded article being irradiated witha laser beam through a transmissive material in another embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First, conventional forms and their problems will be described. Resinmolded articles with localized conductivity are conventionally wellknown that are produced by covering an electrically conductive memberwith insulating resin during molding. According to JP 2012-164447 A, forexample, at least two or more primary assemblies each including aplurality of metal circuit parts installed on a primary molded articleare covered with insulating resin during secondary molding to produce acircuit component. However, this method involves a press step forforming the plurality of metal circuit parts of complex shapes, moldsfor the step, and an installation step for fitting the metal circuitparts to the primary molded article. For this reason, the process iscomplicated to increase the manufacturing costs. Furthermore, with amold having an extremely fine shape compared with the thickness of amaterial, in the press step, the deforming stress applied to the moldwhen the material is pressed to form the above metal circuit parts willsurpass the mold strength and rigidity. Thus, it is challenging to forma complex wiring pattern with a narrow and fine trace-to-trace pitch.

A method of forming a complex wiring pattern is disclosed in JP2006-287016 A. The method is well known to plate the surface of astructure made from insulating resin to form a fine wiring patternwithout using metal circuit parts produced in a press step. However, theplating step is a complex step that includes plating a structure madefrom resin, applying a resist, and forming a wiring pattern with aphotomask. In addition, the plating step involves a liquid wastetreatment step, increasing the manufacturing costs.

As a way of avoiding the above-mentioned increases in costs, JP2000-216521 A discloses a method of partially graphitizing a resinmember by laser irradiation to form an electrical conductor.Specifically, in JP 2000-216521 A, a resin member is irradiated with abeam to selectively graphitize a particular area in a resin surfacelayer, and the resultant carbonized matter is used as a part of thecircuit pattern of a wiring board. However, a sudden increase intemperature produces gas rapidly due to decomposition, causingcarbonized matter to be porous and scatter. In some cases, the generatedgraphite is irregularly aligned. Thus, it is challenging to enhance theelectrical conductivity and the thermal conductivity.

As a way of enhancing the electrical conductivity and the thermalconductivity, JP 2012-223795 A discloses a method of forming a goodelectrically conductive pattern at any site by firing an overall woodymaterial in an oxygen-free atmosphere at relatively low temperaturesfrom 400° C. to 600° C. for 30 minutes to produce carbonized matterhaving some insulating properties, and then irradiating the woodymaterial with a laser beam in the fiber direction. However, the overallcarbonization as pretreatment reduces the strength and the insulatingproperties of a base member compared with the physical properties of theyet-to-be carbonized material. Additionally, preheating takes time andraises the manufacturing costs. Thus, an equivalent or higher electricalconductivity is to be provided in a localized manner within a short timewithout the overall carbonization step. Furthermore, in place of thewoody material, equivalent or higher electrical conductivity is to beimparted to a resin member formed from a strong and heat-resistantengineering plastic material.

As a way of providing graphite with good electrical conductivity andthermal conductivity, JP 2008-24571 A discloses a method of producing agraphite film with good electrical conductivity and thermal conductivityby preparing, as a starting material, a high polymer film material thatis a thin resin member formed by applying solvent to a substrate beforedrying or stretching, and then carbonizing the material. However, if themethod is used for a thick and rigid resin member, gas due todecomposition in the generation process does not readily be emitted,which is likely to cause carbonized matter to scatter. Additionally, itis difficult to align the a-b plane of graphite in the surfacedirection, and predetermined electrical conductivity and thermalconductivity are not easily achieved. Furthermore, overall heattreatment is used in this technique, and thus a localized treatmentmethod is needed to provide electrical conductivity and thermalconductivity in a localized manner.

Among these techniques, the present disclosures suppose that it isuseful to enhance the electrical conductivity of the carbonized matterprovided on the surface of a resin member. However, JP 2000-216521 Adoes not disclose enhancement of the electrical conductivity of thecarbonized matter, and there is room for improvement.

The present disclosure has been made in view of the above, and an objectof the disclosure is to provide a resin member havinghigher-conductivity carbonized matter on its surface, and a method forproducing the resin member.

For carbonized matter close to the surface of a resin member, it isuseful to enhance the electrical conductivity in a direction parallel tothe surface (hereinafter, the surface direction). However, JP2000-216521 A does not disclose the electrical conductivity ofcarbonized matter in a specific direction, and there is room forimprovement. An object of a first aspect of the present disclosure is toenhance the electrical conductivity of carbonized matter formed close tothe surface of a resin member and in particular, enhance the electricalconductivity in the surface direction.

A resin member according to the first aspect of the present disclosureis formed from a resin material containing filler and an insulating basepolymer as a main component. The resin member includes an alignmentlayer close to the surface of the resin member, and the alignment layerincludes filler aligned in the surface direction and a base polymerfilling the space between pieces of the filler. The alignment layerincludes a carbonized portion that is carbonized matter of the basepolymer, contains graphite, and provides electrical conductivity andthermal conductivity.

A method for producing a resin member according to a first aspect of thepresent disclosure includes a molding step and a carbonization step. Inthe molding step, the resin material is molten, and molten resincorresponding to an area close to the surface of the resin member issubjected to shear stress and then solidified to form, close to thesurface, the alignment layer including the pieces of filler aligned inthe surface direction and the base polymer filling the space between thepieces of filler. In the carbonization step, the alignment layer isheat-treated in a localized manner to carbonize the base polymerincluded in the alignment layer, generating the carbonized portionincluding graphite and providing electrical conductivity and thermalconductivity.

According to the first aspect of the present disclosure, the alignmentof the pieces of filler in the surface direction in the alignment layerfacilitates the formation of a layered structure in which the carbonizedmatter generated during the carbonization of the base polymer fillingthe space between the pieces is aligned in the surface direction.Furthermore, the a-b plane of the graphite included in the carbonizedmatter is easily aligned in the surface direction. This enhances theelectrical conductivity of the carbonized matter in the surfacedirection.

When the alignment layer is heat-treated for carbonization in alocalized manner, the filler contained in the alignment layer preventsthe heated site from overheating and slows down the rate of increase intemperature to control sudden generation of gas due to decompositionthat scatters carbonized matter. The filler also anchors the carbonizedmatter or the macromolecules of the base polymer to prevent scatteringof the carbonized matter caused by gas generated due to decomposition.This enhances the fixation of the carbonized matter, improving theelectrical conductivity.

For the carbonized portion including carbonized matter on the surface ofthe resin member, the carbonized matter may be detached during or afterthe production of the resin member to reduce the electrical conductivityof the carbonized portion (i.e., increase the resistance value of thecarbonized portion). An object of a second aspect of the presentdisclosure is to prevent the electric conductivity of the carbonizedportion from decreasing.

A resin member according to the second aspect of the present disclosureincludes a resin material and has a base portion and a carbonizedportion. The base portion includes an insulating base polymer formedfrom a resin material and a filler stronger than the base polymer, andis reinforced by the filler mixed in the base polymer. The carbonizedportion is provided in the outer surface of the base portion and haselectrical conductivity due to carbonized substances included therein.The filler prevents the carbonized portion from being detached from thebase portion, with at least pieces of the filler penetrating thecarbonized portion.

A method for producing a resin member according to the second aspect ofthe present disclosure is a method for producing a resin memberincluding a resin material, and includes a preparation step and acarbonization step. The preparation step includes preparing a baseportion including an insulating base polymer formed from the resinmaterial and filler stronger than the base polymer, and reinforced bythe filler mixed in the base polymer. The carbonization step includesheating the base portion to provide the outer surface of the baseportion with a carbonized portion having electrical conductivity due toincluded carbonized substances obtained by carbonizing a part of thebase polymer such that at least pieces of the filler penetrate thecarbonized portion to prevent the carbonized portion from being detachfrom the base portion.

According to the second aspect of the present disclosure, the fillerprevents the carbonized substances from being lost after the resinmember is produced. This prevents the carbonized portion from decreasingin electrical conductivity due to removal of the carbonized substances.Furthermore, while the base polymer is being carbonized by heating togenerate the carbonized portion, the filler controls scattering of thecarbonized portion caused by generation of gas due to decomposition.This prevents decrease in the electrical conductivity of the carbonizedportion and division of the carbonized portion caused by scattering of apart of the carbonized portion with heating.

Embodiments of resin members that solve the problems with theconventional forms will now be described with reference to the drawings.In the embodiments, substantially the same components are given the samereference numerals, and will not be described redundantly.

First Embodiment

A resin member according to a first embodiment is illustrated in FIGS. 1and 2. A resin member 10 is formed from a resin material containingfiller and an insulating base polymer as a main component. As shown inFIG. 3, the resin member 10 includes an alignment layer 12 close to asurface 11 of the resin member 10. The alignment layer 12 includes manypieces of filler 13 aligned in a direction parallel to the surface 11(hereinafter, the surface direction), and a base polymer 14 filling thespace between the pieces of filler 13.

As shown in FIG. 4, the alignment layer 12 includes a carbonized portion15 that is carbonized matter of the base polymer 14, contains graphite,and provides electrical conductivity and thermal conductivity. In thegraphite composed of carbon atoms bound to each other as shown in FIG.8, one of the four outer shell electrons belonging to each carbon atomremains redundant and free to move, so that the carbonized portion 15 iselectrically conductive.

The resin member 10 has a thickness of 300 μm or more at a site of thecarbonized portion 15 formed. In the first embodiment, as shown in FIG.1, the carbonized portion 15 is formed as multiple straight lines intoan electrically conductive pattern. The electrically conductive patternis, for example, used as circuit wiring in an electronic device such asan air flow meter or a rotation angle sensor. For the carbonized portion15 used in this manner as circuit wiring for carrying electricalsignals, the generated carbonized matter has a volume resistivity of atleast 1.0×10⁻³ Ωm or less, preferably 1.0×10⁻⁴ Ωm or less, and morepreferably 1.0×10⁻⁵ Ωm or less. The carbonized portion 15 may haveanother shape of pattern such as a grid. The carbonized portion 15 maynot be a pattern, but may be formed as a film. The carbonized portion 15is not limited to circuit wiring, but may also be used as, for example,electromagnetic shielding, a static elimination circuit, an antistaticmember, or a heat sink.

A method for producing the resin member 10 will now be described. Asshown in FIG. 5, the method for producing the resin member 10 includesmolding step P1 and carbonization step P2.

<Molding Step (Primary Molding Step)>

In molding step P1, as shown in FIG. 6, a resin material including thefiller 13 and the insulating base polymer 14 is molten at apredetermined plasticizing temperature into molten resin 16, which isthen injected at high speed into a mold 90 with a predetermined shape,and cooled and solidified under pressure. In this process, shear stressis applied between the surface of the mold 90 and the surface of themolten resin 16, or during charging, shear stress is applied between theresin material adhering to the mold surface when the heat is releasedfrom the mold 90, and molten resin 16 with fluidity remains in itscentral area in the thickness direction. As a result, the pieces offiller 13 are aligned preferentially in the surface direction ratherthan the direction normal to the surface, and the base polymer 14 alsoextends between the pieces to form the horizontally charged alignmentlayer 12 close to the surface of a molded article 17.

The filler 13 slows the rate of increase in temperature during theformation of the carbonized portion 15 (see FIG. 4) and also produces ananchor effect on the carbonized matter to prevent carbonized matter fromscattering during carbonization at high temperatures. This enables afine electrically conductive pattern to be formed with accuracy even attemperatures at which carbonized matter in a filler-free natural resinmember would scatter violently and a fine electrically conductivepattern would be difficult to form.

The pieces of filler 13 are desirably aligned in the surface directionin order not to interfere with the electrical connection betweencarbonized substances on the electrically conductive pattern.

The electrical conductivity of the electrically conductive patterngenerated by laser irradiation is much better in a resin membercontaining about 40 wt % glass fiber as the filler 13 than in a resinmember containing no filler 13. The electrical conductivity of theelectrically conductive pattern generated by laser irradiation is betterin a resin member containing about 40 wt % glass fiber as the filler 13than in a resin member containing about 15 wt % glass fiber.Furthermore, the electrical conductivity of the electrically conductivepattern is much better in a laser carbonized area in which the pieces offiller 13 are aligned than in a laser carbonized area in which no filler13 is aligned.

Although the molded article 17 may be produced by, for example,injection molding, transfer molding, extrusion molding, or compressionmolding, injection molding is desirable because greater shearing forcecan be applied to facilitate the formation of the alignment layer 12 inwhich the pieces of filler 13 are arranged more strongly.

As shown in FIGS. 6 and 7, the alignment layer 12 contains the pieces offiller 13 and molecular chains 18 aligned in the surface direction andthe base polymer 14 charged in a manner to extend between the pieces offiller 13 in the surface direction. Thus, the carbonized mattergenerated during carbonization tends to form a layered structure alignedand elongated in the surface direction, enhancing the electricalconductivity and the thermal conductivity in the surface direction. Theshear stress is also applied in the surface direction to themacromolecules forming the base polymer 14, and thus with the molecularchains 18 aligned, the a-b plane of the graphite (see FIG. 8)constituting the carbonized matter is easily aligned in the surfacedirection. This enhances the electrical conductivity and the thermalconductivity in the surface direction. The above effect is particularlyexpected when a thermoplastic resin mainly composed of a chain polymeris to be selected as the base polymer 14.

In the production of the molded article 17, it is appropriate that, inan area to be carbonized, the shearing force during molding be appliedto the surface as much as possible to align the pieces of filler 13 andthe molecular chains 18. It is thus desirable that an area to becarbonized avoid being provided with a weld line or a final fillingportion, and the gate be positioned, shaped, and conditioned so as toavoid the occurrence of jetting. To increase the degree of alignment ofthe pieces of filler 13 and the molecular chains 18 in the moldingprocess, the mold surface may, for example, move to raise the shearstress, or more specifically, slide or rotate. As long as the alignmentlayer 12 is close to the surface of the molded article 17, the moldedarticle 17 may be produced by a method other than a method using aninjection molding machine.

Since the base polymer 14 forming the resin material is carbonized incarbonization step P2, which is the subsequent step, into a graphiticstructure, the base polymer 14 desirably has a high carbon content and acarbocyclic structure similar to the a-b plane of graphite. Examples ofthe base polymer 14 include aromatic condensation polymer materials thatare at least one or more polymers selected from the group consisting ofpolyacrylonitrile, polyacrylic styrene, polyarylates, polyamides,polyamide-imides, polyimides, polyether ether ketone, polyether ketone,polyetherimides, polyether nitrile, polyethersulfone,polyoxybenzylmethylenglycolanhydride, polyoxybenzoyl polyester,polysulfone, polycarbonate, polystyrene, polyphenylene sulfide,polyparaxylene, polyethylene terephthalate, polybutylene terephthalate,polyethylene naphthalate, polyphenylene ether, liquid crystal polymers,bisphenol A copolymers, and bisphenol F copolymers. Aromatic polymersare desirable because they contain, in the main chain, a 6-memberedcarbon ring (i.e., a benzene ring), which forms the basic structure ofgraphite. However, other materials may also be used. Furthermore, forthe purpose of localized carbonization, self-extinguishing materials aremore desirable so as not to cause overburning during carbonization.

In order to deal with gas due to decomposition suddenly generated whenthe heat treatment in carbonization step P2, which is the subsequentstep, causes a sudden temperature increase and carbonization, the filler13 is expected to lower the temperature at a laser beam irradiation spotto slow down the rate of increase in temperature, and to serve as ananchor to prevent scattering of the carbonized matter caused bygenerated gas due to decomposition. The filler 13 thus desirably hasstrength and heat resistance, and a shape with a high aspect ratio. Thatis, the filler 13 is desirably a fibrous substance less flammable thanthe base polymer 14, such as an inorganic fibrous substance. Morespecifically, glass fiber is desirable because of the above propertiesas well as inexpensiveness. When glass fiber is used, the heat treatmentwill melt and solidify the glass to enhance the fixation of thecarbonized matter. Furthermore, for the purpose of localizedcarbonization, the filler 13 may contain an incombustible material thatprovides self-extinguishing properties so as not to cause overburningduring carbonization.

The glass fiber is desirably added in an amount that maximizes theelectrical conductivity and the thermal conductivity. In the case of toolittle glass fiber being added, the fixation of the carbonized matterdue to the anchor effect is insufficient, and heating carbonizationproduces gas due to decomposition suddenly and promotes scattering ofthe carbonized matter, reducing the electrical conductivity and thethermal conductivity. In the case of too much glass fiber being added,the amount of the polymer material relatively decreases, and the densityof the carbonized matter lowers, reducing the electrical conductivityand the thermal conductivity. Thus, when the base polymer 14 used is apolymer with a density of about 1.3 to 1.4 g/cm² in its natural state,such as polyphenylene sulfide, polybutylene terephthalate, polyetherether ketone, or polyoxybenzylmethylenglycolanhydride, the weightproportion of the glass fiber to the entirety, or the weight proportionof the filler 13 to the entire resin member 10 is desirably 30 wt % to66 wt %, preferably 30 wt % to 45 wt %, and more preferably 40 wt %.

Examples of materials for the filler 13 other than glass fiber includeinorganic fibrous substances such as aramid fiber, asbestos fiber,gypsum fiber, carbon fiber, silica fiber, silica-alumina fiber, aluminafiber, zirconia fiber, silicon nitride fiber, silicon fiber, potassiumtitanate fiber, and metal fibrous substances including stainless steel,aluminum, titanium, copper, and brass.

Examples of powdered filling materials include silica, quartz powder,glass beads, milled glass fiber, glass balloons, glass powder, calciumsilicate, aluminum silicate, kaolin, talc, clay, diatomite, silicatessuch as wollastonite, metal oxides such as iron oxide, titanium oxide,zinc oxide, antimony trioxide, and alumina, metal carbonates such ascalcium carbonate and magnesium carbonate, metal sulfates such ascalcium sulfate and barium sulfate, ferrite, silicon carbide, siliconnitride, boron nitride, and other various metal powders. Examples ofmaterials for plate-like filling include mica, glass flakes, and varioustypes of metallic foil. However, other materials capable of fixing thecarbonized matter and forming an alignment layer may also be used.

Highly electrically conductive or thermally conductive filler 13 may beadded to provide electrical conductivity or thermal conductivity to themolded article 17 yet to be carbonized. Also, in this case, carbonizingthe base polymer 14 will enhance the electrical conductivity and thethermal conductivity.

<Carbonization Step>

In carbonization step P2, as shown in FIG. 9, the alignment layer 12close to the surface of the molded article 17 is carbonized by heatingat 1000° C. or more using, for example, laser beam irradiation to cleavebonds in the polymer material and expel constitutive elements other thancarbon as gas due to decomposition including carbon dioxide, carbonmonoxide, nitrogen, and hydrogen. More desirably, the alignment layer 12is heated at 2000° C. or more and partially transformed into graphiteincluding 6-membered carbon rings bound in plane to generate thecarbonized portion 15 including graphite in localized areas on thesurface of the alignment layer 12. The carbonized portion 15 provideselectrical conductivity or thermal conductivity. The carbonizationatmosphere is desirably an inert gas in order to retain as many carboncomponents as possible. Examples of the inert gas include argon andhelium.

Higher temperature heat treatment allows easier transformation into goodgraphite with good electrical conductivity or thermal conductivity.Thus, the heat treatment temperature is desirably 2000° C. or more togive carbonized matter with good electrical conductivity or thermalconductivity. Examples of localized heating methods include laser beamirradiation, plasma treatment, high pressure water vapor application,electron beam irradiation, and Joule heating. Laser beam irradiation isdesirable because it is inexpensive and able to apply heat attemperatures higher than 2000° C. within a short time in a localizedmanner.

As disclosed in JP 2008-24571 A directed to a method of producing agraphite film, in a typical example, laser beam irradiation increasestemperature faster than gradual heating in a furnace that takes a longtime. When a resin is irradiated with a laser beam and heated to a hightemperature suddenly, electrically conductive carbonized matter and gasdue to decomposition are generated. The gas due to decomposition jetsout. The resultant strong impact catches carbonized matter in the gasdue to decomposition, and the carbonized matter is expelled from thesubstrate. In other words, sudden generation of gas due to decompositionscatters carbonized matter significantly. This causes a reduction in theelectrical conductivity and the thermal conductivity of the carbonizedportion 15. In particular, unlike a thin member such as a film, when athick member with a thickness of at least 300 μm or more is carbonized,gas due to internal decomposition cannot easily flow out. The gasflowing out tends to scatter carbonized matter while breaking thestructure. This is a serious cause of reduction in the electricalconductivity and the thermal conductivity.

In the present embodiment, to regulate the above, the filler 13 iscontained in the resin material in a manner to account for apredetermined percentage. The filler 13 slows down the rate of increasein temperature and produces an anchor effect during carbonization. Laserirradiation increases temperature mainly because of the heat generationdue to the absorption of a laser beam and the heat of combustiongenerated when the base polymer 14 carbonizes, and the latter hasgreater influence. When the filler 13 is contained in the resin materialin a manner to account for a predetermined percentage, the base polymer14 decreases relatively to reduce the heat of combustion and slow downthe rate of increase in temperature. The filler 13 fixed in thesubstrate penetrates into or through the carbonized matter like a wedge,producing the anchor effect that prevents the carbonized matter fromseparating from the substrate. The filler 13 is fixed in a resin portionthat is close to the carbonized portion 15 and not to be carbonized orin a resin portion that is positioned forward in the laser scanningdirection on the laser beam path and yet to be irradiated with a laserbeam, and during carbonization by laser irradiation, the fixed filler 13will not allow removal of the carbonized matter caught in the filler 13.In this manner, the carbonized matter is prevented from scattering andcoming off, and the fixation is enhanced.

Since the layer with the pieces of filler 13 aligned in the surfacedirection is formed before carbonization, the polymer filling the spacebetween the pieces of filler 13 is carbonized into a layered structureextending in the surface direction. This enhances the electricalconductivity or the thermal conductivity. In the present embodiment, inmolding step P1, the macromolecules forming the base polymer 14 arealigned in the surface direction by the application of shearing forcewhile molten. As a result, the surface direction and the a-b plane ofthe graphite forming the carbonized matter tend to form a small angle.This enhances the electrical conductivity and the thermal conductivityin the surface direction.

As a laser beam irradiation method to form the finest possible patternwithin a short time, the alignment layer 12 yet to be carbonized may bedirectly scanned only once with a laser beam having a high energydensity (i.e., laser intensity). In some cases, two-stage scanning maybe performed so as to control sudden generation of gas due todecomposition and scattering of carbonized matter as described above.For example, scanning may be performed with a laser beam having arelatively low energy density in a reduced pressure environment toproduce a structure including carbon components as its main components,at a relatively low rate of increase in temperature. Then, a laser beamhaving a high energy density may be applied at a higher temperature toaccelerate the carbonization. In other cases, irradiation may be dividedinto multiple stages as appropriate. After or during the formation of anelectrically conductive pattern with a laser beam, a voltage may beapplied to perform Joule heating in order to promote the carbonization.

As a laser beam path, simple scanning forms a linear pattern. Thescanning evaporates a part of the polymer near the focus of the laserbeam to form a groove. Other scanning methods include a method ofscanning a certain surface without leaving space to form a densecarbonized film on a large area. Also, in this case, a laser beamevaporates a part of the polymer, forming a groove along the laser beampath as irregularities. In laser beam irradiation, the laser beam may bemoved relative to the molded article 17, the molded article 17 may bemoved with the laser beam fixed, or both may be moved.

The laser beam may be of any type as long as it heats a localized areaat a high temperature, and examples of lasers include a CO₂ laser, a YAGlaser, a YVO₄ laser, and a semiconductor laser (GaAs, GaAlAs, GaInAs).To form a fine pattern, a laser beam emitted from a short-wavelengthlaser such as a YAG laser is desirable. To carbonize a large or a deeparea, a laser beam emitted from a long-wavelength laser such as CO₂laser is desirable.

As described above, too high an energy density is not preferable aslaser beam conditions because the spot will overheat and the temperaturewill increase too sharply, generating gas due to decomposition suddenly,scattering carbonized matter. However, too low an energy density is alsonot preferable because the increased temperature is insufficient togenerate graphite. Note that this does not mean laser irradiation ismoderated so as not to burn the filler 13. Immediately below the laserbeam spot, the temperature is very high, and the filler 13 there ismolten or cut. However, the temperature of an area slightly off thelaser beam spot (e.g., the bottom surface and the side surface of agroove) is relatively low, and thus the filler 13 remains. When atypical semiconductor laser is used to start scanning at anapproximately focal length, an output of 100 W and a scan rate of about50 mm/s are desirable. During laser processing, too low an atmosphericpressure is unsuitable because the density of carbonized matterdecreases. Too high an atmospheric pressure is also unsuitable becausegas due to decomposition cannot easily flow out and may break thestructure of carbonized matter. A pressure of 3 MPa or less isdesirable.

As the laser intensity increases or the atmospheric pressure duringlaser processing rises, the volume resistivity of the carbonized portion15 decreases. This is because an increase in temperature at theprocessed area promotes the change of the binding state of the basepolymer 14 to the bonding state of graphitic carbon.

The volume resistivity is an indicator of electrical conductivity perunit volume. That is, in the carbonized portion 15 including carbonizedmatter and the filler 13, as the percentage of the electricallyconductive carbonized matter per unit volume increases, the volumeresistivity decreases. However, too little filler 13 would causecarbonized matter to be caught in gas due to decomposition and scatteredin carbonization step P2. Thus, when the filler 13 is reduced within arange that allows the carbonized matter to be held on the substrate bythe anchor effect, and the percentage of the carbonized matter isincreased, the volume resistivity of the carbonized portion 15decreases.

(Effects)

In the first embodiment, as described above, the resin member 10includes, close to the surface 11, the alignment layer 12 including thepieces of filler 13 aligned in the surface direction and the basepolymer 14 filling the space between the pieces of filler 13. Thealignment layer 12 has the carbonized portion 15 that is carbonizedmatter of the base polymer 14, includes graphite, and provideselectrical conductivity and thermal conductivity.

The alignment of the pieces of filler 13 in the surface direction in thealignment layer 12 facilitates the formation of a layered structure inwhich the carbonized matter generated during the carbonization of thebase polymer 14 filling the space between the pieces is aligned in thesurface direction. Furthermore, the a-b plane of the graphite includedin the carbonized matter is easily aligned in the surface direction.This enhances the electrical conductivity of the carbonized matter inthe surface direction.

When the alignment layer 12 is heat-treated for carbonization in alocalized manner, the filler 13 contained in the alignment layer 12prevents the heated site from overheating and slows down the rate ofincrease in temperature to control sudden generation of gas due todecomposition that scatters carbonized matter. The filler 13 alsoanchors the carbonized matter or the macromolecules of the base polymer14 to prevent scattering of the carbonized matter caused by generatedgas due to decomposition. This enhances the fixation of the carbonizedmatter, improving the electrical conductivity.

In the first embodiment, the resin member 10 has a thickness of 300 μmor more at a site of the carbonized portion 15 formed. Even when such arelatively thick member is carbonized, the filler 13 contained in theresin material in a manner to account for a predetermined percentageslows down the rate of increase in temperature as well as producing ananchor effect during carbonization, preventing the carbonized matterfrom scattering.

In the first embodiment, the weight proportion of the filler 13 to theresin member 10 is 40 wt %. This effectively slows the rate of increasein temperature and produces anchor effect during carbonization,enhancing the electrical conductivity of the carbonized portion 15.

In the first embodiment, the filler 13 is glass fiber. This effectivelyslows the rate of increase in temperature and produces anchor effectduring carbonization, enhancing the electrical conductivity of thecarbonized portion 15. This material is also inexpensive. In addition,the glass is molten and solidified by heat treatment, enhancing thefixation of the carbonized matter.

In the first embodiment, the method for producing the resin member 10includes molding step P1 and carbonization step P2. In molding step P1,the resin material is molten, and molten resin corresponding to an areaclose to the surface 11 of the resin member 10 is subjected to shearstress and then solidified to form, close to the surface 11, thealignment layer 12 including the pieces of filler 13 aligned in thesurface direction and the base polymer 14 filling the space between thepieces of filler 13. In carbonization step P2, the alignment layer 12 isheat-treated in a localized manner to carbonize the base polymer 14included in the alignment layer 12, generating the carbonized portion 15including graphite and providing electrical conductivity and thermalconductivity.

In this manner, the pieces of filler 13 are aligned in the surfacedirection in the alignment layer 12 in molding step P1, facilitating theformation of a layered structure in which the carbonized mattergenerated during the carbonization of the base polymer 14 filling thespace between the pieces is aligned in the surface direction.Furthermore, the a-b plane of the graphite included in the carbonizedmatter is easily aligned in the surface direction. This enhances theelectrical conductivity of the carbonized matter in the surfacedirection.

When the alignment layer 12 is heat-treated for carbonization in alocalized manner in carbonization step P2, the filler 13 contained inthe alignment layer 12 prevents the heated site from overheating andslows down the rate of increase in temperature to control suddengeneration of gas due to decomposition that scatters carbonized matter.The filler 13 also anchors the carbonized matter or the macromoleculesof the base polymer 14 to prevent generated gas due to decompositionfrom scattering the carbonized matter. This enhances the fixation of thecarbonized matter, improving the electrical conductivity.

In carbonization step P2 in the first embodiment, the alignment layer 12is heat-treated in a localized manner by laser beam irradiation. Thisheat treatment allows localized heat application at a high temperaturegreater than 2000° C. within a short time. This enables an electricallyconductive pattern to be formed within a short time at low cost. The useof a laser beam allows the layout of an electrically conductive patternto be changed by simply modifying the scanning software program withoutchanging the hardware. This enables the layout of an electricallyconductive pattern to be changed within a short time at low cost. Forexample, the use of pressed components would require steps of installingand removing molds.

In the first embodiment, the resin material is molded by injectionmolding in molding step P1. This enables relatively large shear stressto be applied to molten resin corresponding to an area close to thesurface 11 of the resin member 10, facilitating the formation of thealignment layer 12 in which the pieces of filler 13 are arranged morestrongly.

Second Embodiment

In a second embodiment, as shown in FIGS. 10 and 11, a resin member 10is not simply flat, but has steps including a first surface 31, a secondsurface 32, and a third surface 33 intersecting each other. Carbonizedportions 15 are formed three-dimensionally from the first surface 31 tothe second surface 32, and from the second surface 32 to the thirdsurface 33. The molded article before carbonization is desirably shapedso that the molten resin in the areas to be carbonized flows in a mannerto align the fillers and the molecular chains with shearing forceapplied as much as possible to the surface during molding. Thus, thefirst surface 31 and the second surface 32 form an outside corner 34shaped as a relatively large R (i.e., rounded), and the second surface32 and the third surface 33 form an inside corner 35 also shaped as arelatively large R. The outside corner 34 and the inside corner 35desirably have the greatest possible radius of curvature. Specifically,at least 5 mm or more is desirable.

As shown in FIG. 12, the surface layer of the resin member 10, that is,an alignment layer 12 has recesses 41. The recesses 41 each have abottom wall 42, which is carbonized into a carbonized portion 15.Between adjacent carbonized portions 15, a rib 43 is formed to enhancethe surface insulation. As such, the inner walls of each recess 41 arecarbonized to provide ribs 43, each of which is between adjacentcarbonized portions 15 to enhance the surface insulation.

In molding step P1 of the production method according to the secondembodiment, as shown in FIG. 13, the recesses 41 are formed in thealignment layer 12 of a molded article 17. In carbonization step P2, thebottom wall 42 of each recess 41 is carbonized by laser beamirradiation. The recess 41 has a groove width W1 greater than thediameter of the convergence laser beam in the recess 41. This enablesthe bottom wall 42 of the recess 41 to be carbonized in a localizedmanner.

Third Embodiment

In a third embodiment, as shown in FIG. 14, a molded article 17 hasrecesses 41 with their bottom surfaces rounded. The shape enhances thedegree of alignment of the fillers and the molecular chains in thebottom wall 42 of each recess 41.

Fourth Embodiment

In a fourth embodiment, as shown in FIG. 15, a molded article 17 hasrecesses 45 each having a bottom wall 42 and a side wall 44, which arecarbonized into a carbonized portion 15. The recess 45 has a groovewidth W2 equal to or smaller than the diameter of the convergence laserbeam at least on the surface of the molded article 17 (i.e., the openingof the recess 45). In the formation of a carbonized portion 15 as anelectrically conductive wiring pattern, the cross-sectional area of thecarbonized portion 15 is desirably increased in the thickness directionof the resin member 10 in order to enhance the electrical conductivitywhile narrowing the trace clearance of the electrically conductivepattern. In the fourth embodiment, the recess 45 is preformed in themolded article 17 yet to be carbonized, and the side wall 44 iscarbonized to increase the cross-sectional area in the depth direction.

To reliably irradiate and carbonize the inside corners of the recess 45with a laser beam, the side wall 44 of the recess 45 has a gradient θgequal to or greater than a laser beam convergence angle θl. In thefourth embodiment, to narrow the trace clearance of the electricallyconductive pattern, the gradient θg of the side wall 44 of the recess 45is approximately equal to the laser beam convergence angle θl. Thisallows the entire wall surface of the recess 45 to be carbonized and theelectrical conductivity to be enhanced. In contrast, in a comparativeembodiment with a recess 81 having a side wall surface 82 that is not agradient as shown in FIG. 16, the inside corners of the recess 81 arenot irradiated with a laser beam, resulting in the formation of dividedcarbonized matter and a lower electrical conductivity.

Fifth Embodiment

In a fifth embodiment, as shown in FIG. 17, recesses 45 are formedinside recesses 41. This allows enhancement of the surface insulationbetween carbonized portions 15 close to each other in the same manner asin the second embodiment, and also enhancement of the electricalconductivity while the trace clearance of the electrically conductivepattern is narrowed in the same manner as in the fourth embodiment.

Sixth Embodiment

In a sixth embodiment, as shown in FIG. 18, recesses 45 are formedinside recesses 41 in the same manner as in the sixth embodiment.However, unlike the sixth embodiment, each recess 45 and the recess 41have a continuous side wall 44. Additionally, the side wall 44 has agradient θg greater than the laser beam convergence angle θl. The recess41 has a groove width smaller than the diameter of the convergence laserbeam at the same level. As a result, the groove including the recess 41and the recess 45 has an inner wall portion that is carbonized in thedepth direction and increases the cross-sectional area, and an innerwall portion that is not carbonized and enhances the surface insulation.In this manner, the recess 41 and the recess 45 may be even with eachother.

Seventh Embodiment

In a seventh embodiment, as shown in FIG. 19, a resin member 10 is aresin body including a resin material and may be used as a housing or acover for an electronic device such as an air flow meter or a rotationangle sensor. The resin member 10 includes a base portion 61 and acarbonized portion 15.

As shown in FIGS. 19, 20, and 21, the base portion 61 includes aninsulating base polymer 14 formed from a resin material and filler 13stronger than the base polymer 14. The base polymer 14 forms the resinportion of the base portion 61. The filler 13 is a reinforcement memberthat reinforces the base portion 61. The base portion 61 is reinforcedby the filler 13 mixed in the base polymer 14.

The carbonized portion 15 is an electrically conductive portion providedin an outer surface 62 of the base portion 61 and having electricalconductivity due to carbonized substances 66 included (see FIG. 8). Thecarbonized portion 15 is formed as multiple straight lines. The multiplecarbonized portions 15 are arranged as a pattern that forms a wiringpattern. The wiring pattern is a current-carrying portion used ascircuit wiring in an electronic device such as an air flow meter or arotation angle sensor.

The carbonized matter is carbon having electrical conductivity (i.e.,electrically conductive carbon). The carbonized matter is formed from acarbonized material that is an electrically conductive material, forexample, a carbon material such as graphite, carbon powder, carbonfiber, a nanocarbon, graphene, or a carbon micromaterial. Nanocarbonsinclude carbon nanotubes, carbon nanofibers, and fullerenes.

As shown in FIGS. 20 and 21, the resin member 10 includes a skin layer63 extending along the outer surface 62 of the base portion 61 and acore layer 64 provided inside the skin layer 63. The skin layer 63 is asurface layer forming the outer surface 62 of the base portion 61 andalso a solidified layer of molten resin solidified in contact with theinner surface of the mold during the resin molding for the base portion61. The core layer 64 is a layer of molten resin fluidized inside thesolidified layer during the resin molding for the base portion 61. Theouter surface 62 of the base portion 61 is the outer surface of the skinlayer 63 and also the outer surface of the resin member 10.

The outer surface 62 has a groove recessed surface 65 formed toward thecore layer 64. The carbonized portion 15 is provided on the grooverecessed surface 65 in a manner to extend from the skin layer 63 towardthe core layer 64. The carbonized portion 15 is obtained by carbonizingat least a part of the skin layer 63. The base polymer 14, which is theresin forming the skin layer 63 and the core layer 64, is formed from amaterial containing at least a 6-membered carbon ring (i.e., a benzenering).

Of the skin layer 63 and the core layer 64, at least the core layer 64forms the base portion 61. In the seventh embodiment, the carbonizedportion 15 is provided in the skin layer 63 apart from the core layer64. In other words, the groove recessed surface 65 does not reach thecore layer 64, with the carbonized portion 15 adjacent only to the skinlayer 63. Both the skin layer 63 and the core layer 64 form the baseportion 61.

As shown in FIGS. 19, 20, and 21, in the skin layer 63, more pieces ofthe filler 13 are aligned in a manner to extend in a predetermineddirection along the outer surface 62 of the base portion 61 than in thecore layer 64. Hereinafter, the filler 13 aligned in a manner to extendin a predetermined direction is referred to as the aligned filler 13.The carbonized portion 15 extends in a direction crossing the alignedfiller 13. In particular, the carbonized portion 15 in the seventhembodiment extends in a direction orthogonal to the aligned filler 13.

As shown in FIG. 22, the carbonized portion 15 is a collection of manycarbonized substances 66. The filler 13 prevents the carbonized portion15 from being detach from the base portion 61, with at least pieces ofthe filler 13 penetrating the carbonized portion 15. In other words, thefiller 13 is a restriction member that prevents the carbonizedsubstances 66 from being detach from the carbonized portion 15. Thefiller 13 may be, as described in the first embodiment, formed from afibrous, a powdered, or a plate-like material. In the seventhembodiment, the filler 13 is formed from a fibrous material such asflame retardant fiber, glass fiber, or carbon fiber, which forms a fiberportion. In FIG. 22, hatching is omitted for clarity.

Of the filler 13 contained in the base portion 61, the pieces protrudingfrom the groove recessed surface 65 strengthen the bonds between thecarbonized portion 15 and the base portion 61, with one end held in thebase portion 61 and the other end trapped in the carbonized portion 15.With the filler 13 formed from a fibrous material, longer portions maybe trapped. In particular, the aligned filler 13, which crosses theextending direction of the carbonized portion 15, easily protrudes fromthe groove recessed surface 65 and is readily caught in the carbonizedportion 15. In addition, pieces of the aligned filler 13 have penetratedthrough carbonized substances 66 in the carbonized portion 15,effectively preventing the carbonized substances 66 from coming off.

A method for producing the resin member 10, as shown in FIG. 23,includes preparation step P1 and carbonization step P2. In preparationstep P1, as shown in FIGS. 24 and 25, the base portion 61 reinforced bythe filler 13 mixed in the base polymer 14 is prepared. The range of thepreparation in preparation step P1 includes molding the base portion 61in the same manner as in molding step P1 according to the firstembodiment, and also providing the premolded base portion 61 that may beunused or used.

In carbonization step P2, as shown in FIGS. 26 and 27, the base portion61 prepared in preparation step P1 is heated. The heating is performedin a manner to provide the outer surface 62 of the base portion 61 withthe carbonized portion 15 that has electrical conductivity due to theincluded carbonized substances 66 obtained by carbonizing a part of thebase polymer 14, and penetrate at least pieces of the filler 13 in thecarbonized portion 15 to prevent the carbonized portion 15 from beingdetach from the base portion 61. The skin layer 63 is heated in a mannerto carbonize at least a part of the skin layer 63 into the carbonizedportion 15 and form the carbonized portion 15 apart from the core layer64.

In carbonization step P2, as shown in FIG. 26, the skin layer 63 isheated in a manner to extend the carbonized portion 15 in a directioncrossing the filler 13 extending in the skin layer 63 along the outersurface 62 of the base portion 61.

(Effects)

As described above, the resin member 10 in the seventh embodimentincludes the base portion 61 and the carbonized portion 15. The baseportion 61 includes the insulating base polymer 14 formed from a resinmaterial and the filler 13 stronger than the base polymer 14, and isreinforced by the filler 13 mixed in the base polymer 14. The carbonizedportion 15 is provided in the outer surface 62 of the base portion 61and has electrical conductivity due to the included carbonizedsubstances 66. The filler 13 prevents the carbonized portion 15 frombeing detach from the base portion 61, with at least pieces of thefiller 13 penetrating the carbonized portion 15.

The method for producing the resin member 10 includes preparation stepP1 for preparing the base portion 61 and carbonization step P2. Incarbonization step P2, the base portion 61 is heated to provide theouter surface 62 of the base portion 61 with the carbonized portion 15that has electrical conductivity due to the included carbonizedsubstances 66 obtained by carbonizing a part of the base polymer 14, andpenetrates at least pieces of the filler 13 in the carbonized portion 15to prevent the carbonized portion 15 from being detach from the baseportion 61.

With the resin member 10 and the method for producing it, the filler 13will not allow the carbonized substances 66 to be detached after theresin member 10 is produced. This prevents the carbonized portion 15from decreasing in electrical conductivity due to detachment of thecarbonized substances 66. Furthermore, while the base polymer 14 isbeing carbonized by heating to generate the carbonized portion 15, thefiller 13 controls scattering of the carbonized portion 15 caused bygenerated gas due to decomposition. This prevents decrease in theelectrical conductivity of the carbonized portion 15 and division of thecarbonized portion 15 caused by scattering of a part of the carbonizedportion 15 with heating.

In the first embodiment, the resin member 10 includes the skin layer 63extending along the outer surface 62 of the base portion 61 and the corelayer 64 provided inside the skin layer 63. Of the skin layer 63 and thecore layer 64, at least the core layer 64 forms the base portion 61. Theouter surface 62 of the base portion 61 has the groove recessed surface65 formed toward the core layer 64. The carbonized portion 15 isprovided on the groove recessed surface 65 in a manner to extend fromthe skin layer 63 toward the core layer 64. In preparation step P1, thebase portion 61 including the skin layer 63 and the core layer 64 isprepared. In carbonization step P2, the skin layer 63 is heated in amanner to carbonize at least a part of the skin layer 63 into thecarbonized portion 15.

In the resin member 10, the filler 13 prevents loss of the carbonizedportion 15 more easily for the skin layer 63, in which the pieces offiller 13 are aligned regularly, than the core layer 64, in which thepieces of filler 13 are aligned rather irregularly. The resin member 10and the method for producing it will thus more effectively prevent thecarbonized portion 15 from being detached from the core layer 64.

With the carbonized portion 15 provided in the core layer 64, the filler13 might fail to prevent the carbonized portion 15 from being detachedfrom the core layer 64 because the pieces of filler 13 are alignedrather irregularly in the core layer 64.

In the first embodiment, however, the carbonized portion 15 is providedin the skin layer 63 apart from the core layer 64. In carbonization stepP2, the skin layer 63 is heated in a manner to form the carbonizedportion 15 apart from the core layer 64. The resin member 10 and themethod for producing it will still more effectively prevent thecarbonized portion 15 from being detached from the core layer 64 sinceno carbonized portion 15 is provided in the core layer 64.

With the filler 13 entirely buried in the carbonized portion 15, thefiller 13 might be detached from the base portion 61 together with thecarbonized portion 15.

In the first embodiment, however, the carbonized portion 15 extends in adirection crossing the filler 13 extending in the skin layer 63 alongthe outer surface 62 of the base portion 61. In carbonization step P2,the skin layer 63 is heated in a manner to extend the carbonized portion15 in a direction crossing the filler 13 extending in the skin layer 63along the outer surface 62 of the base portion 61. With the carbonizedportion 15 and the filler 13 crossing each other in this manner, one endof the filler 13 tends to penetrate the base portion 61 with the otherend caught in the carbonized portion 15, thus preventing the filler 13from being detached from the base portion 61 together with thecarbonized portion 15.

In the first embodiment, the filler 13 has penetrated through thecarbonized substances 66 in the carbonized portion 15. This enables thefiller 13 to prevent loss of the carbonized substances 66 more reliably.For the base polymer 14 with polymer portions (i.e., lumps of polymer)penetrated by the filler 13, heating the base polymer 14 carbonizes thepolymer portions into the carbonized substances 66 with the filler 13penetrated therethrough. On the basis of the phenomenon, the filler 13may be used to prevent scattering of the carbonized substances 66 causedas the base polymer 14 is heated.

Eighth Embodiment

In an eighth embodiment, as shown in FIGS. 28 to 30, a carbonizedportion 15 extends in a direction parallel to aligned filler 13. Incarbonization step P2 (see FIG. 23), as shown in FIGS. 31 to 32, a skinlayer 63 is heated by laser beam scanning in a direction parallel to thealigned filler 13 in a manner to extend the carbonized portion 15 in thedirection parallel to the aligned filler 13. That is, the laser beamscanning direction is parallel to the alignment direction of the alignedfiller 13.

The extension direction of the carbonized portion 15 may not cross thealignment direction of the aligned filler 13 in this manner. As shown inFIG. 31, the filler 13 is fixed in a resin portion that is close to thecarbonized portion 15 and not to be carbonized or in a resin portionthat is positioned forward in the laser scanning direction on the laserbeam path and yet to be irradiated with a laser beam, and duringcarbonization by laser irradiation, the fixed filler 13 will not allowloss of the carbonized matter caught in the filler 13. In this manner,the carbonized matter is prevented from scattering and being lost, andthe fixation is enhanced.

Ninth Embodiment

In a ninth embodiment, as shown in FIG. 33, a resin member 10 includes abase portion 61 having, on its outer surface 62, a first surface 70 as afirst outer surface, a second surface 71 as a second outer surfaceextending in a direction crossing the first surface 70, and a roundedsurface 73 as a rounded outer surface obtained by rounding the partwhere the first surface 70 and the second surface 71 meet (i.e., theinside corner). The outer surface 62 also has a third surface 72 as afirst outer surface extending in a direction crossing the second surface71, and a rounded surface 74 as a rounded outer surface obtained byrounding the part where the third surface 72 and the second surface 71meet (i.e., the outside corner).

A carbonized portion 15 includes a first carbonized portion 75 providedin the first surface 70, a second carbonized portion 76 provided in thesecond surface 71, and a connection carbonized portion 78 provided inthe rounded surface 73 and connecting the first carbonized portion 75and the second carbonized portion 76. The carbonized portion 15 alsoincludes a third carbonized portion 77 provided in the third surface 72,and a connection carbonized portion 79 provided in the rounded surface74 and connecting the second carbonized portion 76 and the thirdcarbonized portion 77.

A comparative embodiment will now be described in which two surfacescross, their corner is not rounded, and the two surfaces are connecteddirectly to each other. In this comparative embodiment, the cornercontains little filler, and the proportion of the base polymer 14 isrelatively high. During laser irradiation, the temperature will thusincrease too sharply, rapidly generating gas due to decomposition andscattering the carbonized matter This may easily break the electricalconnection of the carbonized portion in the corner. Furthermore, as theresin member deforms slightly, stress may concentrate on the corner,physically separating the carbonized portions in the two surfaces, and adisconnection may occur at the carbonized portion in the corner.

In the ninth embodiment, however, the corner between the first surface70 and the second surface 71 is rounded, and the connection carbonizedportion 78 is provided in the rounded surface 73. In addition, thecorner between the second surface 71 and the third surface 72 isrounded, and the connection carbonized portion 79 is provided in therounded surface 74. The connection carbonized portions 78, 79 preventelectrical interruption in the boundary between the first carbonizedportion 75 and the second carbonized portion 76 and the boundary betweenthe second carbonized portion 76 and the third carbonized portion 77.

The method for producing the resin member 10, as shown in FIG. 34,includes preparation step P1, rounding step P2, and carbonization stepP3. In preparation step P1, as shown in FIG. 35, the base portion 61 isprepared that includes three surfaces crossing each other: the firstsurface 70, the second surface 71, and the third surface 72. The partwhere the third surface 72 and the second surface 71 meet is formed asthe rounded surface 74 during the resin molding for the base portion 61.In contrast, the part where the first surface 70 and the second surface71 meet is a sharp corner (i.e., an edge that is not rounded).

In rounding step P2, as shown in FIG. 36, the part where the firstsurface 70 and the second surface 71 meet is rounded to form the roundedsurface 73. The rounding is achieved by eliminating the sharp corner bylaser irradiation.

In carbonization step P3, as shown in FIG. 37, the base portion 61 isheated in a manner to provide the outer surface 62 of the base portion61 with, as the carbonized portion 15, the first carbonized portion 75extending along the first surface 70, the second carbonized portion 76extending along the second surface 71, and the connection carbonizedportion 78 extending along the rounded surface 73 and connecting thefirst carbonized portion 75 and the second carbonized portion 76.Additionally, as the carbonized portion 15, the base portion 61 isheated in a manner to provide the outer surface 62 of the base portion61 with the third carbonized portion 77 extending along the thirdsurface 72, and the connection carbonized portion 79 extending along therounded surface 74 and connecting the third carbonized portion 77 andthe second carbonized portion 76.

A production method will now be described for forming the firstcarbonized portion 75, the second carbonized portion 76, and the thirdcarbonized portion 77 before forming the connection carbonized portions78, 79. In this production method, when the carbonized portion 15 isformed, the first carbonized portion 75 and the second carbonizedportion 76 might not be connected by the connection carbonized portion78, and the second carbonized portion 76 and the third carbonizedportion 77 might not be connected by the connection carbonized portion79.

In the ninth embodiment, however, in carbonization step P3, the baseportion 61 is heated continuously from the first surface 70 to thesecond surface 71 via the rounded surface 73 to connect the firstcarbonized portion 75 and the second carbonized portion W via theconnection carbonized portion 78. In addition, the base portion 61 isheated continuously from the second surface 71 to the third surface 72via the rounded surface 74 so that the second carbonized portion 76 andthe third carbonized portion W are connected by the connectioncarbonized portion 79. As a result, when the carbonized portion 15 isformed, the first carbonized portion 75 and the second carbonizedportion 76 are connected more reliably by the connection carbonizedportion 78, and the second carbonized portion 76 and the thirdcarbonized portion 77 are connected more reliably by the connectioncarbonized portion 79.

Tenth Embodiment

In a tenth embodiment, as shown in FIGS. 38 and 39, a carbonized portion15 is formed as a grid. The carbonized portion 15 is, for example,provided in the outer wall surface of a housing for an electronic devicesuch as an air flow meter or a rotation angle sensor and used as astatic elimination circuit.

A base portion 61 has an outer surface 62 with a deformation 85 providedin a manner to extend along the peripheral edges of the carbonizedportion 15. The deformation 85 is obtained by deforming a part of thebase portion 61. In the tenth embodiment, the deformation 85 resultsfrom melting and solidification. In other embodiments, the deformation85 may result from, for example, removal by machining such as laserprocessing or polishing, or dissolving with a solution. When thecarbonized portion 15 is formed, foreign matter such as scatteredsubstances may adhere to the base portion 61. Even in such a case, theforeign matter may be removed from the base portion 61 when thedeformation 85 is provided. Thus, providing the deformation 85 preventsthe foreign matter from degrading the design quality of the base portion61.

The deformation 85 includes a foamed area 86 in which at least a part ofthe base portion 61 has been foamed, and a plurality of dot-likerecesses 87 provided in the outer surface 62 of the base portion 61. Thefoamed area 86 and the dot-like recesses 87 are deformations that may beprovided by heating the base portion 61.

A method for producing the resin member 10, as shown in FIG. 40,includes preparation step P1, carbonization step P2, and deformationstep P3. In deformation step P3, after carbonization step P2, at least apart of the base portion 61 is deformed to extend the deformation 85along the peripheral edges of the carbonized portion 15 in the outersurface 62 of the base portion 61. In deformation step P3, at least apart of each of the base portion 61 and the carbonized portion 15 isheated at a temperature lower than in the heating of the base portion 61in carbonization step P2, to provide the deformation 85 in the outersurface 62 of the base portion 61.

If foreign matter produced during the heating in carbonization step P2remains on the outer surface 62 of the base portion 61, the foreignmatter may interfere with electric charge emission by the carbonizedportion 15.

In the tenth embodiment, however, the heating in deformation step P3 canburn off the foreign matter remaining on the base portion 61.

If the carbonized portion 15 includes a part that barely remains on thebase portion 61 in an unstable posture, a change in the posture of thepart will vary the ease of passage of electric charge in the carbonizedportion 15. In this case, the electrical conductivity of the carbonizedportion 15 might vary depending on the posture of the part, resulting inunstable electrical conductivity.

In the tenth embodiment, however, when the deformation 85 is provided,the base portion 61 as well as a part of the carbonized portion 15 areremoved. Of the carbonized portion 15, a site in an unstable posture isremoved more easily than a site in a stable posture. More specifically,in deformation step P3, the base portion 61 as well as the carbonizedportion 15 are heated, so that the site of the carbonized portion 15 inan unstable posture can be removed by heating or burning. This enablesvariations in the electrical conductivity of the carbonized portion 15to be suppressed, stabilizing the electrical conductivity of thecarbonized portion 15.

The carbonized portion 15 may also be trimmed to control the resistanceof the carbonized portion 15 to a predetermined value.

In carbonization step P2, the base portion 61 is heated by applying anelectromagnetic wave such as a laser beam to the base portion 61 to formthe carbonized portion 15. In deformation step P3, the base portion 61is heated to provide the deformation 85 by irradiating the base portion61 with an electromagnetic wave at a higher scan rate at a lowerfrequency with a lower intensity (i.e., output) than those of theelectromagnetic wave applied to the base portion 61 in carbonizationstep P2.

In this manner, both the carbonized portion 15 and the deformation 85can be formed by electromagnetic wave irradiation. This reduces theworkload of forming the carbonized portion 15 and the deformation 85.If, for example, carbonization step P2 and deformation step P3 areperformed continuously, the base portion 61 may not be aligned twice ormore with the apparatus that applies electromagnetic waves.

When the deformation 85 is provided using a laser, the resin may foamand change in color depending on the laser energy. However, such foamingand change in color can be caused deliberately in order to providedesign quality. When the deformation 85 is provided using a laser, apulse laser is desirable because of its suitability for removalprocessing. A pulse laser may be used to form the dot-like recesses 87periodically.

Examples will be described below. In each example, for both costefficiency and electrical conductivity, a relatively high-output laserbeam was used to perform processing in a short time. However, forelectrical conductivity enhancement, a relatively low-output laser beammay also be used to perform processing for a long time. In such a case,the rate of rise in temperature will decrease, and the electricalconductivity is expected to increase further.

Example 1

In Example 1, as shown in FIG. 41, the molded article 17 is formed froman insulating resin material having a volume resistivity of 10¹³ Ωm ormore with 40 wt % glass fiber added as filler to a base polymercontaining polyphenylene sulfide as a main component. The alignmentlayer 12 is formed at a depth of at least 0.3 mm or more from thesurface of the molded article 17. As shown in FIGS. 41 and 42, themolded article 17 shaped as a plate with a width and a depth of 80 mm,and a thickness of 3 mm was placed in an argon atmosphere at a pressureof 0.15 MPa, and the alignment layer 12 under a predetermined site onthe surface of the molded article 17 was scanned using a semiconductorlaser adjusted to an approximately focal length to the surface, with anoscillation wavelength of 940 nm and a convergence diameter of 0.6 mm.The laser scanned a 40-mm straight section with an output of 100 W at arate of 50 mm/s to carbonize the part of the alignment layer 12.

As shown in FIGS. 41 and 42, the site on the alignment layer 12irradiated with a laser beam (hereinafter, a first area A1) increases intemperature to about 2,300° C. to 2,500° C., and vigorously generateshot gas due to decomposition. In this state, the resin material foamsinto swellings, while the laser beam evaporates and removes them. As aresult, the first area A1 has a recess, in which carbonized matter has aporous structure.

In parallel, the heat conduction from the hot first area A1 increased intemperature and the hot gas due to decomposition generated from thefirst area A1 form, around the first area A1, a second area A2 thatincreases in temperature to about 1,800° C. to 2,200° C. and becomescarbonized. The second area A2 is off the laser beam scanning directionand not directly irradiated with the laser beam. However, a sitecarbonized under the influence of the temperature of the gas due todecomposition (hereinafter, a third area A3) is not easily evaporated orremoved, and has a raised structure due to foaming and volume expansion(see FIG. 43). The third area A3 yet to be carbonized includes alignedfiller. Based on the alignment state, a carbonized structure was formedas at least ten or more layers elongated in the surface direction (seeFIG. 44).

As shown in FIG. 45, a first layer 21, a second layer 22, and a thirdlayer 23 are observed, with the first layer 21 formed from a resinmaterial containing the aligned filler 13, the second layer 22 foamedand overlying the first layer 21, and the third layer 23 overlying thesecond layer 22 and including carbonized matter layered as describedabove. Within 100 μm in the direction of the normal to the third layer23, a carbonized layer is observed with a multilayer structure includingat least ten or more layers. Under the first area A1 and the third areaA3, the foamed-resin second layer 22 is formed.

Although in FIG. 45, the filler 13 is aligned and the carbonized matteris formed in the same direction, the filler 13 may be strongly alignedin a particular main direction along the resin member surface, and themain direction may be any direction along the resin member surface. Forexample, the filler 13 may be aligned in a direction perpendicular tothe paper of FIG. 45. The carbonized layer and the resin member surfaceform an angle depending on the site carbonized and raised earlier inaccordance with the laser beam scanning direction, and the layer isformed obliquely at some angle with a position upstream in the laserscanning direction being higher (apart from the surface).

In Example 1, the first area A1 and the third area A3 formed anelectrically conductive pattern as a straight line with a width of 0.9mm and a length of 40 mm, and the depth of the carbonization from theresin member surface in the thickness direction was 0.12 mm.Commercially available silver paste was applied to both ends of theelectrically conductive pattern and cured, and the electrical resistancevalue of a 20-mm central part was measured. The electrical resistancevalue across the part was 97.1Ω.

The electrically conductive pattern formed in the first area A1 and thethird area A3 was covered and fixed with a casting made from epoxyresin, and it was confirmed that the electrical resistance of the entirepattern did not vary. Then, the carbonized matter formed in the firstarea A1 was selectively removed from the entire pattern by cross sectionpolishing to give a sample. Based on the relationship between electricalresistances, lengths, and cross-sectional shapes, the electricalconductivity of the carbonized matter formed in the first area A1 wascompared with the electrical conductivity of the carbonized matterformed in the third area A3. The electrical conductivity of thecarbonized matter formed in the first area A1 was three or more times ashigh as the electrical conductivity of the carbonized matter formed inthe third area A3.

Furthermore, the third area A3 was examined by Raman spectroscopicanalysis, and peaks were observed at 1580 cm⁻¹ (G band) and 1360 cm⁻¹ (Dband). The peak intensity ratio of the G band to the D band(I1580/I1360) was 1.61.

The produced carbonized matter was oxidized by letting it stand at roomtemperature for five minutes in nitric acid with a 60% concentration.Then, the nitric acid was washed off with distilled water before theproduct was dried sufficiently in a thermostatic oven at 50° C. Afterthat, when a measurement was conducted in the same manner, theelectrical resistance decreased by 30%.

Example 2

In Example 2, a molded article was formed in the same manner as inExample 1 using an insulating resin material formed from a base polymercontaining polyphenylene sulfide as a main component without filler andhaving a volume resistivity of 10¹³ Ωm or more. The molded article wascarbonized by the same method as in Example 1. In this case, thecarbonized matter was scattered violently and failed to fix. Then, theelectrical resistance was measured by the same method as in Example 1,and the measurement result showed that the value was at least 50 MΩ ormore. Furthermore, the electrical resistance was measured at varyinglaser beam outputs of 5 W, 10 W, 50 W, 100 W, 150 W, and 200 W. At eachoutput, the electrical resistance value was at least 50 MΩ or more.

Example 3

A molded article was formed in the same manner as in Example 1 using anelectrically conductive resin material having a volume resistivity ofabout 10 Ωm with about 30 wt % carbon fiber added as filler to a basepolymer containing polyphenylene sulfide as a main component. The moldedarticle was carbonized by the same method as in Example 1 to form thesame electrically conductive pattern as in Example 1. The electricalresistance was measured by the same method as in Example 1, and themeasurement result showed that the value was 21.8Ω. In addition, thevolume resistivity of the electrically conductive pattern in this statewas roughly calculated at 8.4×10⁻⁵ Ωm based on the length, thecross-sectional shape, and the electrical resistance value.

Example 4

Carbonized matter was formed in the same manner as in Example 1 exceptthat the atmospheric pressure in the laser beam irradiation was reducedto 0.001 MPa. The temperature of generated gas due to decomposition fellinstantly, and little third area A3 was formed, with no layeredcarbonized layer formed in the third area A3 (see FIG. 46). The wiringpattern thus produced had a shape of a straight line with a width of 0.6mm and a length of 40 mm, and the depth of the carbonization from theresin member surface in the thickness direction was 0.05 mm.Commercially available silver paste was applied to both ends of theelectrically conductive pattern and cured, and the electrical resistancevalue of a 20-mm central part was measured. The electrical resistancevalue across the part was 1,124Ω.

Example 5

As shown in FIG. 47, a carbonized portion was formed as a straight linewith a length of 40 mm in the same manner as in Example 1, and thecarbonized portion was formed 50 times with the laser beam scanningdirection shifted each time at intervals of 0.8 mm in the directionvertical to the surface. As a result, the carbonized portions wereelectrically connected linearly to form an electrically conductivepattern that was 40 mm square. The carbonized matter thus produced andthe carbonized matter formed in Example 1 had substantially the sameelectrical conductivity. In this example, irregularities similar tothose in Example 1 were formed in the surface.

Example 6

A molded article was formed in the same manner as in Example 1 using aninsulating resin material having a volume resistivity of 10¹³ Ωm or morewith 33 wt % glass fiber and 33 wt % calcium carbide added as filler,which totaled 66 wt %, to a base polymer containing polyphenylenesulfide as a main component. The molded article was carbonized by thesame method as in Example 1, and the same wiring pattern as in Example 1was formed. The electrical resistance was measured by the same method asin Example 1, and the measurement result showed that the value was1,270Ω.

Example 7

A molded article was formed in the same manner as in Example 1 using aninsulating resin material having a volume resistivity of 10¹³ Ωm or morewith 30 wt % glass fiber added as filler to a base polymer containingpolyphenylene sulfide as a main component. The molded article wascarbonized by the same method as in Example 1, and the same wiringpattern as in Example 1 was formed. The electrical resistance wasmeasured by the same method as in Example 1, and the measurement resultshowed that the value was 139.3Ω.

Example 8

A molded article was formed in the same manner as in Example 1 using aninsulating resin material having a volume resistivity of 10¹³ Ωm or morewith 45 wt % glass fiber added as filler to a base polymer containingpolyphenylene sulfide as a main component. The molded article wascarbonized by the same method as in Example 1, and the same wiringpattern as in Example 1 was formed. The electrical resistance wasmeasured by the same method as in Example 1, and the measurement resultshowed that the value was 169.1Ω.

Example 9

A molded article was produced by compression molding using an insulatingresin material having a volume resistivity of 10¹³ Ωm or more with 35 wt% glass fiber and 15 wt % other inorganic filler as filler, whichtotaled 50 wt %, to a base polymer containing phenol resin as a maincomponent. Then, the molded article was carbonized by the same method asin Example 1 to form a pattern with a width of 0.75 mm and a length of40 mm, and the depth of the carbonization from the resin member surfacein the thickness direction was 0.05 mm. In this state, the electricalresistance value of a 20-mm part was measured in the same manner as inExample 1. The electrical resistance value was 171.2Ω.

Example 10

A molded article was produced by injection molding using the same resinmaterial as in Example 9. Then, the molded article was carbonized by thesame method as in Example 1 to form the same electrically conductivepattern as in Example 9. In this state, the electrical resistance valueof a 20-mm part was measured in the same manner as in Example 1. Theelectrical resistance value was 133.3Ω.

Example 11

A carbonized matter was formed in the same manner as in Example 1 exceptthat the atmospheric pressure in the laser beam irradiation wasincreased to 1.0 MPa. The electrically conductive pattern formed had anelectrical conductivity improved by 30% compared with Example 1.

Example 12

The molded article formed in the same manner as in Example 1 wassubjected to 1.5-mm wet abrasion on the surface in the thicknessdirection to remove the alignment layer. Then, on the resin membersurface, after being dried sufficiently, carbonized matter was formed inthe same manner as in Example 11, and the same electrically conductivepattern as in Example 1 was formed. In this state, the electricalresistance value of a 20-mm part was measured in the same manner as inExample 1. The electrical resistance value was 558Ω.

Example 13

As shown in FIG. 48, the alignment layer 12 of a molded article 17formed in the same manner as in Example 1 was brought into close contactwith a metallic member 51 such as iron, copper, or brass. Under the sameconditions as in Example 1, a laser beam was applied to a contactinterface 52 between the alignment layer 12 and the metallic member 51to form a carbonized portion 15 as shown in FIG. 49. The carbonizedportion 15 and the metallic member 51 were electrically connected toeach other sufficiently.

Example 14

As shown in FIG. 50, a molded article 17 was formed from the same resinmaterial as in Example 1 with a predetermined area thinned to about 0.1mm, and the thin area was brought into close contact with a metallicmember 51. Under the same conditions as in Example 1, a laser beam wasapplied to the metallic member 51 and the thin area of the moldedarticle 17 in the thickness direction to form the carbonized portion 15as shown in FIG. 51. The carbonized portion 15 corresponding to the thinarea reached the metallic member 51 in the thickness direction, and thecarbonized portion 15 and the metallic member 51 were electricallyconnected to each other sufficiently.

When a carbonized portion is formed in the contact interface between thealignment layer of a molded article and a metallic member, the resin ofthe alignment layer may not be heated for carbonization, but themetallic member may be heated to serve as a heat source for carbonizingthe alignment layer.

Although the metallic member used in the above method is not limited toa particular material, the selection of a metal that easilysolid-solubilizes carbon, such as nickel, bismuth, or iron, leads toparticularly good bonding and electrical connection. In particular, theuse of nickel is particularly effective because catalysis occurs in theinterface to form high-quality graphite. In some cases, iron is alsoeffective since it reacts with carbon to form an electrically conductivecompound depending on the temperature and the amount of carbon supplied.Such a kind of metal may be added to the surface of the metallic memberby plating or other method.

Example 15

When the carbonized matter formed in Examples 1 to 14 was covered withan epoxy resin casting, the electrical conductivity of the carbonizedmatter did not change, and a resin member with an internal patternhaving good electrical conductivity was obtained.

Other Embodiments

In another embodiment, the carbonized portion may not be a pattern, butmay be formed as a film. In this case, the resin member may have, on itssurface, an electrically conductive film denser than a resin memberprovided with electrical conductivity by mixing and dispersingelectrically conductive filler in a resin material. This enables theresin member to have better electromagnetic shielding. A thick resinmember that is 300 μm or more in thickness may have higher electricalconductivity and thermal conductivity as well as better electromagneticshielding.

In another embodiment, the carbonized portion may not be provided apartfrom the core layer. More specifically, the carbonized portion may reachthe core layer through the skin layer. In the core layer, the fillertends to be aligned irregularly. However, at least pieces of the fillermay penetrate the carbonized portion to prevent the carbonized portionfrom being detach from the base portion.

In another embodiment, the entire outer surface of the resin member maybe provided with a planar carbonized portion. Moreover, the carbonizedportion may reach the core layer through the skin layer. In this case,the base portion is composed of the core layer.

In another embodiment, the amount of filler added and the heatingconditions may be modified to adjust the electrical resistance value,and the product may be used as a resistor or a heater in an electricaldevice.

In other embodiment, to further enhance electrical conductivity andthermal conductivity, the carbonized matter formed in the surface of aresin member may be used as an electrode and electroplated. Furthermore,to enhance electrical conductivity, an oxidizing agent may be used tocause oxidation.

In another embodiment, to form a complex electrically conductivepattern, every surface of a molded article may be provided with anelectrically conductive pattern. For example, with a through hole madein the molded article, the electrically conductive patterns formed onboth sides of the through hole may be electrically connected bycarbonizing the inside of the through hole or inserting an electricallyconductive member.

In another embodiment, to form more complex multilevel crossing, resinmembers 10 may be each produced by providing carbonized portions 15 inpredetermined positions as shown in FIG. 53 in a molded article 17formed as shown in FIG. 52, and the plurality of resin members 10 may beintegrated as shown in FIG. 54 by, for example, fitting such as pressfitting or snap fitting, bonding, welding, or insert molding.Furthermore, to prevent the carbonized matter from coming off, acovering 53 that covers and secures the carbonized matter may be formedas shown in FIG. 55 by, for example, insert molding, potting, applying acuring agent, covering, or other method. In this state, some pieces ofthe filler have penetrated the carbonized matter and protrude from theresin members 10. Thus, when the protruding pieces of the fillerpenetrate the covering 53, which is a secondary molded article, theresin members 10 and the covering 53 have higher adhesion.

In another embodiment, to prevent the carbonized matter from coming off,a part of the resin forming the molded article may be molten by heatingto encase the carbonized matter. The heat source for the heating may bea laser beam.

In another embodiment, a layer of a material that transmits a laser beam(transmissive material) may be formed on the surface of a molded article17 before carbonization. As shown in FIG. 56, a laser beam may beapplied to a molded article 17 through a transmissive material 55 toform a carbonized portion 15 between the molded article 17 and thetransmissive material 55. It is desirable to provide a channel betweenthe molded article 17 and the transmissive material 55 for release ofgas due to decomposition by, for example, providing a porous layerbetween the molded article 17 and the transmissive material 55 orforming irregularities on the surface of the molded article 17 or thetransmissive material 55.

Although carbonized matter and another metallic member may be simplybrought into contact with each other to establish electrical connectionbetween them, in another embodiment, electrically conductive adhesivesuch as silver paste or carbon paste or molten metal such as solder maybe applied between the carbonized matter and the metallic member.

In another embodiment, the laser used in the carbonization step may alsobe used to debur the resin member or perform printing on it.

The present disclosure has been described based on the embodiments.However, this disclosure is not limited to the embodiments andconfigurations. The disclosure encompasses various modifications andalterations falling within the range of equivalence. Additionally,various combinations and forms as well as other combinations and formswith one, more than one, or less than one element added thereto alsofall within the scope and spirit of the present disclosure.

What is claimed is:
 1. A resin member including a resin material, theresin member comprising: a base portion including an insulating basepolymer formed from the resin material, and filler, the fillercomprising a fibrous material and being stronger than the base polymer,and the base portion being reinforced by the filler mixed in the basepolymer; and a carbonized portion provided in an outer surface of thebase portion and having electrical conductivity due to carbonizedsubstances included therein, wherein the filler prevents the carbonizedportion from being detach from the base portion, with at least pieces ofthe filler penetrating the carbonized portion.
 2. The resin memberaccording to claim 1, further comprising: a skin layer extending alongthe outer surface of the base portion; and a core layer provided insidethe skin layer, wherein of the skin layer and the core layer, at leastthe core layer forms the base portion, the outer surface of the baseportion has a recessed surface being recessed toward the core layer, andthe carbonized portion is provided on the recess in a manner to extendfrom the skin layer toward the core layer.
 3. The resin member accordingto claim 2, wherein the carbonized portion is provided apart from thecore layer in the skin layer.
 4. The resin member according to claim 2,wherein the carbonized portion extends in a direction crossing thefiller extending in the skin layer along the outer surface of the baseportion.
 5. The resin member according to claim 1, wherein the outersurface of the base portion has first outer surfaces, a second outersurface extending in a direction crossing the first outer surfaces, androunded outer surfaces obtained by rounding parts where the first outersurfaces and the second outer surface meet, and the carbonized portionincludes first carbonized portions provided in the first outer surfaces,a second carbonized portion provided in the second surface, andconnection carbonized portions provided in the rounded outer surfacesand connecting the first carbonized portions and the second carbonizedportion.
 6. The resin member according to claim 1, wherein the outersurface of the base portion has a deformation obtained by deforming atleast a part of the base portion, the deformation extending alongperipheral edges of the carbonized portion.
 7. The resin memberaccording to claim 6, wherein the deformation includes at least one of afoamed portion in which at least a part of the base portion is foamed,and a plurality of recesses provided in the outer surface of the baseportion.
 8. A method for producing the resin member of claim 1 includingthe resin material, the method comprising: a preparation step ofpreparing the base portion including the insulating base polymer formedfrom the resin material, and filler, the filler comprising the fibrousmaterial and being stronger than the base polymer, and the base portionbeing reinforced by the filler mixed in the base polymer; and acarbonization step of heating the base portion to provide the carbonizedportion in the outer surface of the base portion, the carbonized portionhaving electrical conductivity due to included carbonized substancesobtained by carbonizing a part of the base polymer such that at leastpieces of the filler penetrate the carbonized portion to prevent thecarbonized portion from being detached from the base portion.
 9. Themethod according to claim 8, wherein: the preparation step includespreparing the base portion including a skin layer extending along theouter surface of the base portion, and a core layer provided inside theskin layer, and the carbonization step includes heating the skin layerto carbonize at least a part of the skin layer into the carbonizedportion.
 10. The method according to claim 9, wherein the carbonizationstep includes heating the skin layer to form the carbonized portion notbeing in contact with the core layer.
 11. The method according to claim9, wherein the carbonization step includes heating the skin layer toextend the carbonized portion in a direction crossing the fillerextending in the skin layer along the outer surface of the base portion.12. The method according to claim 8, further comprising: a rounding stepof forming rounded surfaces in the base portion including, on the outersurface, first surfaces and a second surface extending in a directioncrossing the first surfaces, the rounded surfaces being obtained byrounding parts where the first surfaces and the second surface meet,wherein the carbonization step includes heating the base portion toprovide the outer surface of the base portion with, as the carbonizedportion, first carbonized portions extending along the first surfaces, asecond carbonized portion extending along the second surface, andconnection carbonized portions extending along the rounded surfaces andconnecting the first carbonized portions and the second carbonizedportion.
 13. The method according to claim 12, wherein the carbonizationstep includes heating the base portion continuously from one of eachfirst surface and the second surface to the other via the roundedsurface to connect the first carbonized portion and the secondcarbonized portion via the connection carbonized portion.
 14. The methodaccording to claim 8, further comprising after the carbonization step, adeformation step of deforming at least a part of the base portion toextend a deformation obtained by deforming at least a part of the baseportion, along peripheral edges of the carbonized portion in the outersurface of the base portion.
 15. The method according to claim 14,wherein the deformation step includes heating at least a part of each ofthe base portion and the carbonized portion at a temperature lower thana temperature in the heating of the base portion in the carbonizationstep, to provide the deformation in the outer surface of the baseportion.
 16. The method according to claim 14, wherein the carbonizationstep includes heating the base portion by applying an electromagneticwave to the base portion to form the carbonized portion, and thedeformation step includes heating the base portion is heated to providethe deformation by irradiating the base portion with the electromagneticwave at an intensity lower than an intensity of the electromagnetic waveapplied to the base portion during carbonization.